{"id":"CVE-2026-104851","title":"fsspec is a specification and Python implementation framework for filesystem interfaces","summary":"fsspec is a specification and Python implementation framework for filesystem interfaces. From 0.9.0 until 2026.6.0, fsspec.implementations.reference.ReferenceFileSystem evaluates fields from Kerchunk reference JSON documents through unre…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cwe":["CWE-94","CWE-1336"],"vendor":"fsspec","product":"filesystem_spec","affected":["filesystem_spec >= 0.9.0, < 2026.6.0"],"published":"2026-10-02","updated":"2026-10-02","sourceUpdated":"2026-10-02T17:17:03.763","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-104851","references":[{"url":"https://github.com/fsspec/filesystem_spec/commit/86438783f93b1398ef245b92f0e6063b445b611c","label":"security-advisories@github.com"},{"url":"https://github.com/fsspec/filesystem_spec/commit/a1c16ab3f07f354aa371c38f7b1b07ea7fd4c5c8","label":"security-advisories@github.com"},{"url":"https://github.com/fsspec/filesystem_spec/pull/2029","label":"security-advisories@github.com"},{"url":"https://github.com/fsspec/filesystem_spec/pull/2039","label":"security-advisories@github.com"},{"url":"https://github.com/fsspec/filesystem_spec/releases/tag/2026.6.0","label":"security-advisories@github.com"},{"url":"https://github.com/fsspec/filesystem_spec/security/advisories/GHSA-27vj-qcqg-25rc","label":"security-advisories@github.com"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-10-02T17:24:03.905Z","slug":"CVE-2026-104851","body":"## Overview\n\nfsspec is a specification and Python implementation framework for filesystem interfaces. From 0.9.0 until 2026.6.0, fsspec.implementations.reference.ReferenceFileSystem evaluates fields from Kerchunk reference JSON documents through unrestricted jinja2.Template(...).render(...) calls in _process_references1._render_jinja, _process_templates, and _process_gen in fsspec/implementations/reference.py. A document supplied inline or fetched from an attacker-controlled URL can provide template expressions that execute Python code when the reference filesystem is opened, including through consumers such as xarray, before referenced data is read. The _process_gen path is reached whenever a document includes a gen array, while the other paths depend on template-related options and values. This issue is fixed in version 2026.6.0.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}